As a biological material, wood is subject to attack by fungi and insects. These organisms may damage the appearance of the wood, and they may seriously reduce it's structural strength. Wood and wood-based products can be protected from the effects of wood destroying organisms by applying fungicides or insecticides, or both. Such treatments can greatly improve the service life of the wood product, especially for timbers with low natural durability, such as radiata pine and other softwood species.
For some wood-based products, conventional methods of applying preservative treatment are inappropriate. For example, water based treatments such as copper chrome arsenate (“CCA”) cannot be applied to laminated veneer products, particle based products or fibre based products without causing significant degrade and product loss. Other post-manufacture treatments for these products, such as light organic solvent preservative (“LOSP”) are expensive and require a further processing step to achieve the treatment, creating extra cost.
A method favored by some wood-based product manufacturers is the application of a preservative by addition to the glue during manufacture. This approach can be used for any wood product that is constructed from relatively thin or small particles, such as wood fibre, wood chip or flake and thin wood veneer. Plywood, laminated veneer lumber (LVL), medium density fibreboard (MDF), waferboard/strandboard/oriented strandboard (OSB) and particleboard fall into this category.
The major drawbacks with this method of application lie in the nature of the glues used in the manufacturing process and the type of compounds available for treatment.
In general, glue systems for wood based products have high pH (9-12) or are highly reactive (e.g. isocyanate based glues). Thus the addition of a compound to such an environment can result in rapid degradation of the molecule. A further challenge to the robustness of the added compound is the curing condition for the glues. These are often high temperatures (˜170° C.) in a high pressure pressing system.
These conditions require that any added preservative be robust enough to retain at least some of it's activity to be effective during the service life of the product.
It is known in the art that triazoles are generally effective against the Basidiomycetes, which are the fungi known to cause decay in wood. The triazoles most commonly used to protect solid wood from decay are tebuconazole and propiconazole. The amount of active ingredient needed in the wood to protect from decay has been shown to be in the order 50 g/m3 wood to 300 g/m3 wood for tebuconazole and 220 g/m3 wood to 490 g/m3 wood for propiconazole. It has also been disclosed that these two triazoles can act synergistically in some cases.
Furthermore, it is also known that due to the nature of the glue systems, the above mentioned triazoles that show activity in solid wood applications, when used in a glue-line treatment, have to be added in large quantities to the glue mixture due to subsequent breakdown in the process or due to inhomogeneous distribution in the wood based product.
A need therefore continues to exist for a preservative for wood-based products that can be applied in the manufacturing of wood-based products.
Applicant has surprisingly found that triadimefon and triadimenol can be used as preservatives for the protection of wood-based products against attack and destruction of microorganisms, especially of fungi.
Surprisingly triadimefon and triadimenol are stable under the conditions of the glue-line treatment and thus can be employed as preservatives in the manufacturing of glued wood-based products. In some cases, under alkaline conditions, triadimefon is being converted into triadimenol which is stable under these conditions and which also exhibits the required biological properties.